Earth moving equipment, such as bulldozers generally includes a chassis, a working tool (bucket, blade, grab, drill etc), a protective driver cabin with access door, and some form of access or access system, such as fixed or moveable ladder or stair. The chassis includes all the mechanical parts that form the structural frame of the earth moving equipment. The driver operates the earth moving equipment from the protective driver cabin. A hatch is located behind the driver cabin and typically houses many of the important control units of the earth moving equipment vehicle such as hydraulic controls, hydraulic pump, fuse box, electrical circuit breakers etc. The access device provides access between the ground level and the cabin. Typically, though not always present, walkways are provided around the cabin area for an operator to access the hatch located behind the driver cabin of the earth moving equipment vehicle. The access device is usually attached to the walkway, chassis or cabin structure near the entry door to the cabin.
Retractable access systems of different configurations are presently known and have two final positions, namely the deployed position and the retracted position. The major types of access devices are the vertical variable height access system and the swing access system.
The vertical variable height access system would generally be used for large excavators and earth moving equipment. In the vertical variable height access system, the ladder or stairs would be operated vertically and would remain vertical both in the deployed position and retracted position. Essentially, the length of the ladder or stairs does not vary, rather, the ladder or stairs is simply lifted vertically upwards or lowered downwards.
In the swing type access system, the ladder or stairs when operated will swing (rotate) up or down to reach either the retracted position or deployed position respectively.
The basic constituents of any access system include a ladder or stairs and a mechanism to actuate the ladder or stairs. The ladder or stairs are generally made of metal such as steel or aluminium. The movement of the ladder or stairs in any access system is controlled by an actuator mechanism. The actuator mechanism moves the ladder or stairs between the deployed and the retracted position. This actuator is usually operated either mechanically, electrically or hydraulically. A combination of these means is also in practice.
Problems exist with certain types of earth moving equipment. For example, graders have at least one large blade used for levelling earth, soil, sand etc. The blade can be lifted/lowered, rotated and tilted, to allow for an initial level of the surface to be graded and/or to impart a required level to the surface. Basically the blade is set at a required angle, and the vehicle advanced over the surface such that the blade forms a particular slope or level to the surface. This is particularly prevalent when forming a level or particular sloping surface for the sides of new access roads where banks are required in virgin soil that is initially uneven. Graders are also used to re-level loose surface roads that incur holes, washout due to flooding or other disturbances that degrade the surface. These vehicles have a cabin for the operator immediately behind the blade. This position allows the operator to oversee the blade position and grading as the vehicle advances. However, because the cabin is above and between the blade to the front and the rear wheel behind, any access means has to extend downwards between the blade and rear wheel to permit access/egress. The blade of a grader is sufficiently maneuverable that the access means can be damaged or removed by impact from the blade swinging against the access means. In addition, for rotational retracting access means, because of limited space adjacent the side of the cabin, the operator's cabin door must be latched fully open or closed to avoid the access means damaging or removing a partially open door as it rotates to deploy/retract. Either instance can result in injury to the operator or other person, downtime of the vehicle and increased cost to the operator.
With the aforementioned in mind, it would be desirable to provide a retractable access device for earth moving equipment that is space saving in a retracted position, and preferably less prone to being damaged during operation.
A preferred object of the present invention would be to provide a retractable access device that does not affect the opening or closing of the cabin door of earth moving equipment.